Insulin and hydrocortisone, but not triiodothyronine, are required for the differentiation of pig preadipocytes in primary culture.

The objective of this study was to establish optimal conditions for the primary culture of pig preadipocytes. We cultured pig preadipocytes for 10 d and studied the effects of insulin, hydrocortisone, and triiodothyronine (T3) added to serum-free basal medium on differentiation and gene expression of lipoprotein lipase an early marker, and adipsin, a late marker of preadipocyte differentiation. Insulin alone and hydrocortisone alone stimulated a low level of cell differentiation, as indicated by an increase in glycerol-3-phosphate dehydrogenase activity. When added together, insulin and hydrocortisone had a synergistic effect on cell differentiation. When combined with insulin or hydrocortisone, T3 had no effect on cell differentiation, indicating that T3 is not required in porcine preadipocyte culture. Gene expression studies also showed that removal of insulin or hydrocortisone from complete serum-free medium reduced both early and late marker mRNA. As expected, removal of T3 had no effect on the gene expression of early and late marker mRNA. We conclude that insulin and hydrocortisone, but not T3, are required for the differentiation of pig preadipocytes in primary culture.